Pressure switch with adjusting cam of particular configuration

ABSTRACT

A pressure-responsive switch assembly, particularly suitable for use in automatic washing machines, embodying a fluid-pressureresponsive diaphragm, a switch arm operated by movement of the diaphragm, a pair of contacts selectively engageable by the switch arm depending upon the position of the diaphragm, with biasing means for applying a variable biasing force on the diaphragm in opposition to the fluid pressure acting thereon, in combination with a cam having its periphery in camming engagement with the biasing means, the cam having a projection thereon arranged to depress the biasing means sufficiently to move the switch arm from engagement with one of the contacts to a reset position in which it engages the other of the contacts, with means for rotating the cam in one direction only, the cam being so formed as to provide incremental changes in the pressure on the biasing means upon rotation thereof so that rotation of the cam through one complete revolution serves to momentarily place the switch assembly in its reset position.

United States Patent [72] lnventor Douglas A. Heaps Saint Joseph, Mich.

211 App]. No. 875,426

[22] Filed Nov. 10, 1969 [45] Patented Sept. 28, 1971 [73] Assignee Whirlpool Corporation Benton Harbor, Mich.

[54] PRESSURE SWITCH WITH ADJUSTING CAM OF PARTICULAR CONFIGURATION 5 Claims, 4 Drawing Figs.

[52] US. Cl 3200/83WM, 68/207, 337/319, 337/323 [51] Int. Cl H0lh 35/34 [50] Field of Search 200/83, 83

WM, 83.9,153.11,153.13,166 M; 337/319, 323, 57, 67, 94, 367, 368, 347; 68/12, 23.5, 207

Assistant Examiner-Robert A. Vanderhye Attorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: A pressure-responsive switch assembly, particularly suitable for use in automatic washing machines, embodying a fluid-pressure-responsive diaphragm, a switch arm operated by movement of the diaphragm, a pair of contacts selectively engageable by the switch arm depending upon the position of the diaphragm, with biasing means for applying a variable biasing force on the diaphragm in opposition to the fluid pressure acting thereon, in combination with a cam having its periphery in camming engagement with the biasing means, the cam having a projection thereon arranged to depress the biasing means sufficiently to move the switch arm from engagement with one of the contacts to a reset position in which it engages the other of the contacts, with means for rotating the cam in one direction only, the cam being so formed as to provide incremental changes in the pressure on the biasing means upon rotation thereof so that rotation of the cam through one complete revolution serves to momentarily place the switch assembly in its reset position.

PRESSURE SWITCH WITH ADJUSTING CAM OF PARTICULAR CONFIGURATION CROSS-REFERENCE TO RELATED APPLICATIONS This application has subject matter in common with Mason application Ser. No. 735,270 filed June 7, I968, now U.S. Pat. No. 3,498,091 and Mason et al., Ser. No. 741,763 filed July 1, 1968, both assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION l. Field of the Invention This invention is in the field of pressure-responsive switch assemblies provided with means for selectively biasing the switch assembly to provide a wide range of control, and provided with means for ensuring that the switch goes through a reset operation when it is desired to change the operating level of the switch from a lower pressure to a higher pressure condition.

2. Description of the Prior Art Automatic washing machines frequently make use of a pressure-responsive switch to enable the user to preselect a water level in the tub appropriate to the amount of fabrics being laundered in the tub.

Pressure-responsive switches which employ some form of reset mechanism have been described in the prior art but are not entirely satisfactory because they require a conscious effort on the part of the user to go through the reset operation when adjusting the liquid level in the tub to a value different from that which was originally preset. For example, in US. Pat. No. 2,934,6l8 there is an adjustment type of pressure switch in which three discrete levels can be selected by the actuation of a control shaft. This device makes use of a cam which operates on a lever to adjust the axial position of a bolt which presets the pressure at which the switch mechanism becomes operative. In order to change the level of water in the machine after it has begun operation, it is necessary to reset the switch mechanism to make it responsive to a higher water level. This type of switch assembly, however, is limited in the amount of adjustability which is provided in the water level in thetub.

US. Pat. No. 3,267,232 also discloses a pressure-responsive switch employing a cam to change the level at which the switch becomes operative. In order to change levels in a washing machine incorporating such a pressure switch, a lever must be actuated to one extreme of the cam in order to effect resetting of the switch mechanism. Consequently, with this typeof structure, if the operator merely changes the position of the selector level without moving it entirely to one end in order to reset the switch, there will be no change in the water level.

A different type of pressure-responsive switch is illustrated in U.S. Pat. No. 3,291,932 which makes use of several types of reset mechanism which involve either a push-to-reset or a pull-to-reset structure.

SUMMARY OF THE INVENTION The pressure-responsive switch of the present invention provides an incremental control to preset the response level of a pressure switch, utilizing a cam which is rotatable in one direction only and in which a portion of the cam provides reset action with the remainder of the 360 are providing an incremental control over an extended range for the water level in the tub. In the structure of the present invention, operation of the level control automatically brings the reset mechanism into operation when the pressure switch is changed to secure a higher water level after machine operation has begun. This is accomplished by providing, in combination with a conventional pressure-responsive switch, a cam which imposes a variable bias on the pressure-responsive diaphragm, the cam having a projection thereon which is arranged to put the switch assembly into its reset position, and in which a one-way drive means is provided on the cam to ensure that the switch will be reset in passing from a lower liquid level to a higher liquid level after machine operation has begun.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a somewhat schematic view of a pressure-responsive switch assembly as it has been employed in prior art washing machines;

FIG. 2 is a rear elevational view of a switch-setting mechanism according to the present invention;

FIG. 3 is a side elevational view of the assembly shown in FIG. 2; and

FIG. 4 is a fragmentary front elevational view of the assembly shown in FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the showing of FIG. 1, reference numeral 10 indicates generally a washing machine including an imperforate tub II in which there is disposed at perforate, rotatable basket [2. A centrally disposed agitator I3 is driven in an oscillatory fashion by means of a motor 14 acting through a transmission 15. Water is introduced into the tub by means of an inlet conduit 16 under the control of a solenoid-operated valve 17.

Pressure conditions in the tub are sensed at an outlet port 18 connected by means of a flexible tube 19 to an inlet port 20 of a pressure-responsive switch assembly generally indicated at reference numeral 21. The particular pressure-responsive switch assembly shown in FIG. I is typical of those used in the prior art, wherein the flexure of a diaphragm is employed to selectively move a switch contact arm from engagement with one to engagement with another pair of stationary switch contacts. In the particular type of switch assembly shown in FIG. I, as the fluid level in the tub II rises, air in the conduit 19 is compressed, and enters a chamber 22 where it acts upon a flexible diaphragm 23 confined within the switch assembly 21. A post 24 acts against the rearward end of the diaphragm 23 in opposition to the fluid pressure acting on it from the chamber 22. The post 24 is biased against the diaphragm 23 by a compression spring 25. The spring 25 is preloaded by means of a plunger 26, with the pressure thereon being determined by the setting of a follower screw 27 which engages the plunger 26, and whose relative pressure against the plunger 26 is varied by a cam 28. The amount of preloading acting against the diaphragm 23 is determined by the relative position of the cam and varies from a low point on the cam to a high point 29 by which maximum pressure is exerted. The position of the cam 28 relative to the follower screw 27 is determined by a control knob 30 on the console of the washing machine, the control knob 30 being coupled to the cam 28 through a mechanical linkage generally indicated at numeral 31 of the drawing. Thus, if the control knob 30 is set at a high water level position, the cam 28 biases the plunger 26 to a low position with a relatively high portion of the cam 28 riding on the follower 27. In this position, the spring 25 exerts a strong force on the diaphragm 23 by means of the post 24. It then requires a high degree of air compression in the chamber 22 to overcome the biasing force. At the other extreme, when the cam 28 engages the follower at its low point, the relatively small amount of air pressure in the chamber 22 will be effective to move the diaphragm 23.

The diaphragm 23 controls the position of a switch arm 32 which is mounted in cantilever fashion within the switch housing. The switch arm 32 is arranged to move between a pair of stationary contacts 33 and 34 depending on the position of the diaphragm 23. A C" spring 35 acts as a toggle spring, and has one end connected to a center tongue 36 of the switch arm 32. Upon movement of the post 24 caused by flexure of the diaphragm, the C" spring 35 is moved into an overcenter position, causing a toggle action to occur in moving the switch arm 32 from contact 33 to contact 34.

With the tub ll empty, the switch arm 32 of the pressure switch assembly engages contact 33 to close the circuit to the solenoid-operated valve 17, thereby permitting water to enter the tub through the inlet conduit 16. After the water level in the tub reaches a height detennined by the setting of the control knob 30, the diaphragm 23 is deflected enough to cause the switch arm 32 to shift from contact 33 to contact 34, thereby energizing the motor 14 and deenergizing the solenoid-operated valve 17. Thus, water introduction is terminated and the agitator l3 begins to operate.

Normally, the control knob 30 will be set at some position which is intermediate the lowand high-level points. After the tub 11 has been filled to the predetermined level, further additions of water cannot be made until the switch arm 32 is reset so that it is in engagement with the contact 33. To accomplish this, it is necessary to move the control knob 30 to the reset" position whereupon the high point 29 of the cam engages the follower 27 forcing the plunger to its extreme lowermost position, thereby flexing the diaphragm to the bottom of the chamber 22. This amount of movement is sufficient to snap the spring 35 back over center and the switch arm 32 thereby moves from contact 34 to contact 33 permitting the solenoidoperated valve 17 to again become operative. Then, the operator can move the control knob 30 to a higher position and change the maximum water level in the tub.

The improved switch-actuating mechanism of the present invention is illustrated in FIGS. 2 to 4, as applied to the pressure switch assembly 21 of the type shown in FIG. 1. Mounted atop the pressure switch assembly 21 is a bracket 37 including a pair of spaced parallel upstanding leg portions 38 and 39, and a base portion 40 secured to the pressure switch assembly. A control shaft 41 is journaled for rotation between the upstanding leg portions 38 and 39, the shaft 41 having a flat portion 42 which is arranged to receive a control knob on the face of the control panel of the washing machine. Fixedly secured to the shaft 41 is a cam 43 whose configuration is best seen in FIGS. 2 and 4 of the drawing. The cam 43 is arranged to ride against an arm 44 secured to the leg portion 39 and at the end of which there is an adjustment screw 45. The screw 45 bears down on the plunger 26 of the pressure-responsive switch assembly 21.

As best seen in FIGS. 2 and 4, the periphery of the cam 43 is eccentric with respect to the axis of the shaft 41. Consequently, when the shaft 41 is rotated, the periphery of the cam 43 causes the arm 44 to move up and down, the motion of the arm 44 being guided by a slot (not shown) suitably formed in the upstanding arm 38. The movement of the arm 44 therefore causes the follower screw 45 to bear down on the plunger 26 with varying amounts of pressure and provides a varying bias against which the diaphragm 23 acts.

A ratchet wheel 46 is fixedly secured to the cam 43 or to the shaft 41. The ratchet wheel 46 cooperates with a resiliently biased pawl 47 consisting of a resilient arm having an end portion 48 engaging teeth 49 on the ratchet wheel 46. The ratchet wheel 46 is thus arranged to move in one direction only, this being clockwise in FIG. 4 and counterclockwise as shown in FIG. 2.

The cam 43 has a projection 50 thereon arranged to depress the arm 44 sufficiently so that through the follower screw 45, the plunger 26 and the spring 35, the switch arm 32 in the switch assembly is moved from contact 34 to contact 33, thereby resetting the switch assembly.

As seen in FIGS. 2 and 4, the cam 43 has a configuration such that it has a low point 51 immediately before and a high point 52 immediately after the projection 50 in the direction of rotation of the cam. Consequently, when the selector knob 30 is rotated through the reset position the plunger 26 will be exerting the maximum amount of pressure against the diaphragm 23 in opposition to the fluid pressure acting on the diaphragm. The tube is then capable of being filled to a higher level than that originally preset, and once, the level reaches the desired new level, the operator turns the control knob 30 until the fluid pressure from the chamber 22 overcomes the bias provided by the plunger 26 and the spring 25, thereby deenergizing the solenoid l7 and terminating introduction of water into the tub.

From the foregoing, it will be understood that the pressureresponsive switch assembly of the present invention provides a control which can preset the response level of a pressure switch over a substantial portion of the periphery of the cam. With the switch arrangement of the present invention, it is necessary to pass the reset position of the switch in order to adjust the control to a position representing a higher water level, without going through an extraneous resetting operation.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a pressure-responsive switch assembly having a fluidpressure-responsive diaphragm,

a switch arm operated by movement of said diaphragm,

a pair of contacts selectively engageable by said switch arm depending on the position of said diaphragm, and

biasing means for applying a variable biasing force on said diaphragm in opposition to the fluid pressure acting thereon, the improvement which comprises a cam having its periphery in camming engagement with said biasing means,

said cam having a projection thereon arranged to depress said biasing means sufficiently to move said switch arm from engagement with one of said contacts to a reset position in which it engages the other of said contacts, said cam having a low point immediately before and a high point immediately after said projection in the direction of rotation of the cam, means for rotating said cam in one direction only, said cam providing gradual changes in the pressure on said baising means upon rotation thereof, along substantially its entire periphery, whereby rotation of said cam through one complete revolution serves to momentarily place said switch assembly in its reset position.

2. The switch assembly of claim 1 in which said means for rotating said cam in one direction only includes a pawl and ratchet.

3. The switch assembly of claim 2 in which said ratchet is secured to said cam and is rotatable therewith.

4. A washing machine comprising a tub,

inlet means for introducing water into said tub,

solenoid means controlling operation of said inlet means,

an agitator disposed in said tub,

a motor arranged to drive said agitator,

an adjustable pressure-responsive switch form sensing the level of liquid in said tub, said pressure-responsive switch including manually operable control means,

a switch arm,

a pair of contacts selectively engageable by said switch arm, the engagement of said switch arm with one of sad contacts in a first position functioning to energize said solenoid means and introduce water in said tub, the engagement of said switch arm with the other of said contacts in a second position functioning to deenergize said solenoid means and energize said motor,

a diaphragm responsive to the liquid level in said tub and arranged to move said switch arm into one of said two positions,

biasing means acting on said diaphragm to set the operating point at which said arm engages said one or said other of said contacts,

a cam having its periphery in camming engagement with said biasing means, said cam having a projection thereon arranged to act on said biasing means with sufficient pressure to cause said switch arm to move from engagement with said other contact to said one contact, said cam having a configuration such that it has a low point immediatetion of a 360 are.

5. The washing machine of claim 4 in which said means for rotating said cam in one direction only includes a pawl and ratchet.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 609, 272 Dated Sepgember 28, 1971 InventorQ) Douglas A. Heaps It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 4, line 50, "form" should be --for--;

line 58, "sad" should be --said--;

Signed and sealed this 9th day ofMay 1972.

(SEAL) Attest:

EDWARD M.FLE'ICHER,JR. ROBERT GOITSGHALK Attesting Officer Commissioner of Patents FORM poloso USCOMM-DC 60376-P09 9 U 5 GOVERNMENT PRINTYHG DFFICE: 19. 0").33 

1. In a pressure-responsive switch assembly having a fluidpressure-responsive diaphragm, a switch arm operated by movement of said diaphragm, a pair of contacts selectively engageable by said switch arm depending on the position of said diaphragm, and biasing means for applying a variable biasing force on said diaphragm in opposition to the fluid pressure acting thereon, the improvement which comprises a cam having its periphery in camming engagement with said biasing means, said cam having a projection thereon arranged to depress said biasing means sufficiently to move said switch arm from engagement with one of said contacts to a reset position in which it engages the other of said contacts, said cam having a low point immediately before and a high point immediately after said projection in the direction of rotation of the cam, means for rotating said cam in one direction only, said cam providing gradual changes in the pressure on said baising means upon rotation thereof, along substantially its entire periphery, whereby rotation of said cam through one complete revolution serves to momentarily place said switch assembly in its reset position.
 2. The switch assembly oF claim 1 in which said means for rotating said cam in one direction only includes a pawl and ratchet.
 3. The switch assembly of claim 2 in which said ratchet is secured to said cam and is rotatable therewith.
 4. A washing machine comprising a tub, inlet means for introducing water into said tub, solenoid means controlling operation of said inlet means, an agitator disposed in said tub, a motor arranged to drive said agitator, an adjustable pressure-responsive switch form sensing the level of liquid in said tub, said pressure-responsive switch including manually operable control means, a switch arm, a pair of contacts selectively engageable by said switch arm, the engagement of said switch arm with one of said contacts in a first position functioning to energize said solenoid means and introduce water in said tub, the engagement of said switch arm with the other of said contacts in a second position functioning to deenergize said solenoid means and energize said motor, a diaphragm responsive to the liquid level in said tub and arranged to move said switch arm into one of said two positions, biasing means acting on said diaphragm to set the operating point at which said arm engages said one or said other of said contacts, a cam having its periphery in camming engagement with said biasing means, said cam having a projection thereon arranged to act on said biasing means with sufficient pressure to cause said switch arm to move from engagement with said other contact to said one contact, said cam having a configuration such that it has a low point immediately before and a high point immediately after said projection in the direction of rotation of the cam, means coupled with said control means for rotating said cam in one direction only, said cam providing gradual changes in the pressure on said biasing means upon rotation thereof through a major portion of a 360* arc.
 5. The washing machine of claim 4 in which said means for rotating said cam in one direction only includes a pawl and ratchet. 